yes, many converted and manufactured bikes run this motor, see Easgen (Denzel). They use the same motor.

User called Skeetab78 sketab778 or something.. can't remember right now; he is converting light motorcycle with this 7.5kw motor. It's in the testing phase.

Another person from Russia is manufacturing own frame (basically motorcycle) to be used with this motor but he plans to add gearbox, few speeds, gearbox is the same as rickshaw trikes use.

There is some guy from (in usa) attached this motor to regular fat bicycle via regular bicycle gears. Insane dynamic.

If you want little bit more powerful than this motor you can approach QS; they got similar but heavier ~1.5kg and longer. They have pulleys if you need; they use it with pulleys, not sprockets and chains.

The motor is sold by Cyclone and Easgen.
Easgen has lathed axle in their motor sold with freewheel which puts on motor axle so your motor won't spin when you realease gas; oh and it is 420 which is good if you want it for motorcycle.

Regarding it's power output. It's up to 10kw, peaks.
Regular controller settings coupled with this motor look like this - 72v 70A battery amps; maybe up to 90A if overpowered.

QS use their motor with up to 20% to 30% more Amps. QS put their motor in scooters and 12'' rim ~120/70 tyre motorcycles/scooters, Monkey bikes. 20Teeth front, 103teeth rear pulleys.

Kilometres per hour.
Speeds, up to 120 in speed gearing.
Speeds up to 70 for torque, offroad.
Bikes weight usually up 70kg with this motor (battery and rest included, without driver).

Q: Do I need a license to ride the ECR V1?
A: Yes, you need a license to ride the ECR. By May-June 2018 ECR will be street legal in the USA and Australia, and we will do our best to get ECR homologated in EU by August 2018. Without registration ECR is't street legal.

I missed that, but I posted on their Facebook page that I hoped it would be street legal and, within about an hour, they sent me an email saying exactly what you quoted. I think I'll forget the conversion idea. With the speed at which things are developing now, it would probably be foolish to piece something together and then find I could buy a professionally built cycle for the same price or even less.
They're buying all the components at wholesale and I'd be paying retail.

2)Perhaps I could simply flip the rear wheel over to put the sprocket on the right hand side. There is a lever for the rear (drum) brake, which would then be on the wrong side, but I could probably run a cable in place of the rod.

Will your drum brake operate correctly rotating in reverse?

(will it grab correctly/sufficiently, or will it grab too hard and be unable to let go, etc).

FWIW, 7500w may not be much power, depending on the size/weight, and acceleration and speeds required. For most, it's probably enough.

I missed that, but I posted on their Facebook page that I hoped it would be street legal and, within about an hour, they sent me an email saying exactly what you quoted. I think I'll forget the conversion idea. With the speed at which things are developing now, it would probably be foolish to piece something together and then find I could buy a professionally built cycle for the same price or even less.
They're buying all the components at wholesale and I'd be paying retail.

Manufacturer gets parts for a wholesale price but when they sell them they ask more than as if were bought for retail prices plus more, of course, as it's their business.
Retail price compared to wholesale is 20-30 %. It costs way more than 20-30 % when it is in one piece; also it is road legal; plus shipping; plus tax when it arrives to EU/USA; most probably they will be shipped from CN at the beginning.
You DIY cheaper if you get right rolling chases and skills, but the question is final bike weight and registration to be road legal; their frame is lighter then most 125cc and even some 50cc. When you do yourself it is trial and error, experiment, but when you get from a manufacturer it is been tested therefore you don't need to do it yourself.